1. Field of the Invention
The present invention relates to an optical head capable of adapting to an optical information reproducing device, which reproduces the information recorded on an optical recording medium or an opto-magnetic recording medium.
2. Related Art Statement
As a conventional example of an optical head capable of adapting to an optical information reproducing device, which reproduces the information recorded on an optical recording medium or an opto-magnetic recording medium, the optical head is disclosed, for example in Japanese patent application opened Nos. 177,643/92, 35,737/89, Articles 28a-SF-11 and 28a-SF-12 disclosed in the 54th Applied Physics in Japan.
In the optical head shown in Japanese patent application opened No. 177,643/92, a prism (micro-prism) is disposed on a optical detecting means, a wave plate is adjoined to an oblique plane of the prism and a polarizing film is provided to the surface of the wave plate, an outgoing light from a semiconductor laser diode (LD) is reflected on the polarizing film to illuminate the recording medium, and the reflected light from the recording medium is detected by the optical detecting means through the polarizing film, the wave plate and the prism, thereby reproducing the information signals recorded on the recording medium.
In the optical head shown in Japanese patent application opened No. 35,737/89, the beam emanated from the light generating element is illuminated on the recording medium (disk) through first and second diffracting lattices which are disposed so as to cross the lattice arranging direction to each other, the emanated light from the recording medium is incident on first and second light receiving elements having light path difference through the second diffracting lattice, and the reproduced signal and error signal (tracking error signal) are obtained. As shown in FIGS. 6A and 6B of the above Japanese patent application opened No. 35,737/89, this conventional example utilizes a microprism in order to obtain the above light path difference, so that it constructs a planar optical head of 3 beam system without using a beam splitter.
In the conventional example shown in the above article, the semiconductor laser (LD), the photodetector (PD),the polarizing holograph and the opto-magnetic signal detecting micro-prism are accommodated in the same package and modularized to intend to downsize the optical head.
In the examples shown in Japanese patent application opened No. 177,643/92 and the above Article, the micro-prism (the prism constructed on the semi-conductor substrate together with other elements) having a size smaller than that of the prism utilized as the optical element of single body is utilized, so that it is impossible to work the micro-prism. Moreover, the micro-prism is formed on the surface of the photo-detector, so that it is necessary to perform the centering control and the position fixing of the micro-prism while observing the signals from the photodetector in practice, and thus very precise assembling and adjusting technique is required, thereby causing an increase of production cost.
While in the conventional example of the above Japanese patent application opened No. 35,737/89, the micro-prism is used to obtain the optical path difference, so that the same problem as in the above in accompany with the micro-prism arises. In addition thereto, this conventional device does not use a polarization separating function, so that the opto-magnetic signal can not be reproduced, and thus it is impossible to adapt the opto-magnetic information signal reproducing device.